Thermodiazo copying process

ABSTRACT

A THERMALDIAZO COPYING MATERIAL AND PROCESS THEREFOR WHERIN A HYDRAZONE COMPOUND DECOMPOSES UPON HEATING TO FORM A HETEROCYLIC METHYLENE BASE COMPOUND CAPABLE OF COUPLING WITH A DIAZONIUM COMPOUND TO FORM AN AZO DYE IMAGE.

United States Patent U.S. Cl. 96-49 8 Claims ABSTRACT OF THE DISCLOSURE A thermaldiazo copying material and process therefor wherein a hydrazone compound decomposes upon heating to form a heterocylic methylene base compound capable of coupling with a diazonium compound to form an azo dye image.

The present invention relates to compounds, materials and processes for recording and reproducing information. More particularly the present invention is concerned with diazotype copying.

Several attempts have been made to manufacture a single sheet thermodiazo copying material. A survey of systems suited for thermodiazocopying is given by B. Friedland, I. Phot. Sci., vol. 10, 1962, pp. 174-177. According to one of the systems described therein use is made of materials that are not couplers by themselves but that are capable of forming couplers under the influence of heat. The present invention relates to such system according to which a special type of heat-sensitive latent coupler is used, wherefrom a coupler can be produced by heating, said coupler needing no alkali for coupling with a diazonium compound.

More particularly there has been found a thermodiazoprocess wherein an active methylene base suited for coupling with a diazonium compound is produced by heating of an hydrazone compound corresponding to the following general formula:

wherein Z represents the necessary atoms to close an aromatic nucleus, e.g. a benzene nucleus including a substituted benzene nucleus, e.g. a benzene nucleus substituted with a C -C alkyl group, a phenyl group, an acyl group such as an acetyl group, a hydroxyl group, an alkoxy group such as a methoxy group, or an acetoxy group, and

R represents an aliphatic group including a saturated, an unsaturated, a cycloaliphatic and a substituted aliphatic group, e.g. an alkyl group, more particularly a C -C alkyl group, a cyclohexyl group, a cyclopentyl group, an allyl group, a substituted alkyl group, e.g. an aromatically substituted alkyl group, e.g. a benzyl group, a hydroxyalkyl group, a carboxyl-substituted alkyl group, a sulpho-substituted alkyl group or an acetoxy-substituted alkyl group, wherein the alkyl group preferably contains from 1 to 4 carbon atoms.

3,563,744 Patented Feb. 16, 1971 Ice It is assumed that by heating said hydrazone compound a methylene base is produced according to the following reaction scheme:

The hydrazone compounds according to the above general formula are prepared by reaction of the corresponding hydrazine with methyl isopropyl ketone.

The temperature at which the methylene base can be formed with the hydrazone compound in the presence of a diazonium compound is in general comprised between 70 and 140 C.

According to a preferred embodiment the hydrazone compound and a suitable diazonium compound are incorporated into a single sheet material, wherein the methylene base coupler can be produced by heat and come into effective contact with the diazonium compound. By effective contact is meant that the methylene base coupler in the heating step can react with the diazonium compound in order to form therewith a dye.

The following general preparation method is illustrative for the preparation of the hydrazone compounds used according to the present invention.

1 mole of the elected hydrazine derivative and 1.5 mole of methyl isopropyl ketone are dissolved in 1500 cos. of ethanol containing 10 cos. of glacial acetic acid. The mixture is refluxed for 3 hours. In a sample taken after that period of time free hydrazine should not be detected any longer by reduction of ammoniacal silver nitrate solution.

The ethanol is removed by evaporation and the residue distilled under reduced pressure. The boiling points vary between 70 and 150 C. at 1 mm. Hg. The yields are approximately Hydrazone compounds particularly suited for use according to the present invention are the compounds having the following formulae:

CH CHzCHeOH Exemplary diazo compounds are the diazonium salts obtained by diazotation of the following amines:

pamino-N,N-dimethylaniline p-amino-N,N-diethylaniline p-amino-N-ethyl-N-fi-hydroxyethylaniline p-amino-N-ethyl-N-benzylaniline p-amino-phenyl-morpholine p-amino-(2,5-diethoxy)-N-benzoylaniline p-amino-(2,5-dibutoxy)-N-benzylaniline 4-amino-(2,5-dimethoxy)-4'-methyldiphenyl sulphide p-amino-o-ethoxy-N,N-diethylaniline p-amino-ochloro-N,N-diethylaniline Suitable supports or carriers used in copying materials according to the present invention are absorbent materials, e.g. ordinary wood pulp paper or rag type paper but also textiles including fabrics made of cotton, cellulose acetate, regenerated cellulose, in other words all types of woven or felted materials that can be impregnated with a solution containing (an) hydrazone compound(s), a diazonium compound or a mixture of diazonium compounds.

For producing transparent diazo prints it is preferred, however, to apply the hydrazone compound to a transparent sheet, e.g. a water-impermeable resin sheet, as used, e.g., in transparent photographic silver halide materials. In this case the chemicals are preferably incorporated into a hydrophilic colloid layer, e.g. in a gelatin layer.

The coating composition containing a hydrazone compound and a diazonium compound may contain other ingredients, e.g., wetting agents, optical brightening agents, pigments, and antioxydants improving the whiteness of the areas, in which the diazonium compound has been destroyed. Suitable antioxydants are urea, thiourea, ascorbic acid and allyl isothiocyanate in concentrations ranging from 25 to 15 percent by weight in respect of the diazonium salts.

The storage stability of the coating composition containing (a) hydrazone compound(s) and (a) diazonium compound(s) can be improved by the addition of an acid e.g. citric acid, tartaric acid, boric acid, trichloroacetic acid, tribromoacetic acid, sulphosalicylic acid, phosphoric or 1,3,5-naphthalene-trisulphonic acid used in an amount of 1 to percent by weight in respect of the diazonium salt.

It is self-explanatory that all known principles for preventing premature coupling can be applied in order to obtain a recording material with a storage stability as high as possible.

So, a premature coupling can be further prevented by physically separating the diazonium salt and the couplergenerating compound by means of a layer consisting of a meltable resinous material, Which prevents the chemicals from coming into effective contact before heating. The resinous layer is melted by heating, which allows the chemicals to dilfuse therein and react. For example a porous paper is first imbibed with the hydrazone compound and then dried. To the dried paper a meltable resin layer, e.g. a hydrophobic alkyd resin is coated from a solution and dried. Particularly suitable results can be obtained by the use of rosin or a rosin ester such as an ester gum (see for ester gum, EllisThe Chemistry of Synthetic Resins, p. 793 (1935), Reinhold Publishing Corporation). This coated sheet is then treated with a diazonium compound either or not in the presence of a hydrophilic binding agent, e.g. ethylcellulose.

According to another embodiment applied for preventing a premature coupling one of both of the reagents are encapsulated. By encapsulation the chemicals are enveloped in a thin continuous water-impermeable shell consisting, e.g., of a resinous material as described in the UK. patent specifications 1,048,696 and 1,048,697. The non-encapsulated reagent is preferably applied in a continuous phase of hydrophilic colloid.

In connection with the present invention the term thermodiazo process includes any information-recording process, according to which said hydrazone compound is used in combination with a diazonium compound, and wherein an azo dye is formed by starting from said compounds by means of heat.

Such information-recording process includes more particularly a first thermodiazo copying process comprising (1) the image-wise or record-wise exposure of a recording material containing a diazonium compound and a said hydrazone compound to ultra-violet radiation, and (2) the non-differential heating of the image-wise -U.V.-exposed recording material so that an azo dye is formed in correspondence with the non-U.V.-exposed areas of the recording material. The information-wise recording process also includes a second thermodiazo copying process comprising (1) the image-wise or record-wise heating of a recording material containing a diazonium compound and a said hydrazone compound so that an azo dye is formed in correspondence with the image-wise heated areas of the recording material, and (2) the non-differential exposure of the image-Wise heated recording material to ultra-violet radiation in order to stabilize the image.

The following examples illustrate the invention.

EXAMPLE 1 A solution consisting of:

Zinc chloride double salt of N,N-dimethylaminobenzene-diazonium chloride 1 1,3,5-naphthalene trisulphonic acid 5 Urea 18 Water to 100 ccs.

was coated on a paper base material impregnated with N'-(2,3-dimethyl 2 propanone) N methylphenylhydrazone and then dried. After drying, the recording material was exposed for 30 sec. through a positive silver image transparency by means of a high pressure mercury vapour bulb of W. placed at a distance of 15 cm. The development was carried out by contacting the exposed recording material with a heated drum (about 130 C.). An apparatus containing such drum is a Dry Silver M 107 sold by Minnesota Mining and Manufacturing Company, St. Paul, Minn., U.S.A.

EXAMPLE 2 A solution as described in Example 1 was made except that the zinc chloride double salt of N-hydroxyethyl-N- methyl-aminobenzene-diazonium chloride was used instead of the zinc chloride double salt of N,N-dimethylamino-benzene-diazonium chloride. Processing was the same as that described in Example 1.

EXAMPLE 3 A solution as described in Example 1 was prepared except that 2 g. of N'-(2,3-dimethyl-2-propanone)-N-hydroxyethylphenylhydrazone were used instead of N'-(2,3- dimethyl 2 propanone) N-methylphenylhydrazone. Processing was the same as that described in Example 1.

EXAMPLE 4 A solution as described in Example 1 was prepared except that instead of ccs. of water, 100 ccs. of 10% aqueous solution of gelatin were used. The obtained solution was coated onto a transparent polyethylene terephthalatesupport and the coating dried at room temperature by an air current.

The processing was the same as that described in Ex ample 1.

We claim:

1. A diazotype process wherein a visible image is formed in a diazotype material comprising a support having a diazonium compound and a hydrazone compound coated thereon, said hydrazone compound produces an azo coupling component for the diazonium compound upon heating, said hydrazone compound corresponding to the following general formula:

wherein:

Z represents a benzene nucleus and R represents a lower alkyl group, the process steps comprising either (A) (1) imagewise heating of the diazotype material so that an azo dye image is formed in the heated areas of the said material and (2) non-differentially exposing said material to ultra-violet radiation in order to stabilize the said image, or (B) (1) imagewise exposing of the diazotype material with ultra-violet radiation and (2) non-dilferentially heating the said material to form an azo dye image in the areas not exposed to ultra violet radiation.

2. A process according to claim 1, wherein a recording material containing a diazonium compound and the hydrazone compound is information-wise exposed to ultra-violet radiation, and the exposed recording material is non-differentially heated to form a coupler from the said quaternary heterocyclic nitrogen compound for the diazonium compound.

3. A process according to claim 1, wherein a recording material containing a diazonium compound and the hydrazone compound is image-wise heated, and the imagewise heat-exposed recording material is non-diiferentially exposed to ultra-violet radiation.

4. A process according to claim 1, wherein the hydrazone compound and the diazonium compound are applied to an absorbent support.

5. A process according to claim 1, wherein the hydrazone compound is incorporated into an absorbent support and is shielded from intimate contact with the diazonium compound by an intermediate meltable resin layer.

6. A process according to claim 1, wherein the hydrazone compound is encapsulated in a continuous waterimpermeable meltable resin shell, and the diazonium compound as well as the capsules are incorporated into a continuous hydrophilic binder film layer on said support.

7. A process according to claim 1, wherein the diazonium compound is encapsulated in a continuous water-impermeable meltable resin shell, and the hydrazone compound as well as the capsules are incorporated into a continuous hydrophilic binder film layer on said support.

8. A diazotype copying material comprising a support having a diazonium compound and a hydrazone compound coated thereon, said hydrazone compound corresponding to the following general formula:

wherein:

Z represents a benzene nucleus, and R represents a lower alkyl group.

References Cited UNITED STATES PATENTS OTHER REFERENCES Dietzger, J. E.: Reprods Review, February 1962, pp. 14, 15, 22 and 26.

NORMAN G. TORCHIN, Primary Examiner C. L. BOWERS, IR., Assistant Examiner U.S. Cl. X.R. 

